1. Field of the Invention
The present invention relates to portable circular saws, and in particular to portable circular saws that have a saw unit inclining mechanism for laterally inclining a saw unit with respect to a workpiece. In particular, portable circular saws can perform bevel-cutting operations using a saw blade that is laterally inclined relative to a base that contacts a workpiece.
2. Description of the Related Art
Known portable circular saws comprise a base adapted to contact a workpiece, and a saw unit that has a circular saw blade. The saw blade has a lower portion that can protrude downward through and from the base so as to cut the workpiece. The circular saw unit can vertically pivot relative to the base (in a direction perpendicular to the rotational axis of the saw blade), so that the downward protruding distance of the saw blade from the base can be changed. Thus, the cutting depth can be adjusted. In addition, the circular saw can laterally pivot relative to the base (in a lateral direction with respect to the saw blade), so that a bevel cutting operation can be performed with the saw blade laterally inclined relative to the workpiece. The incline angle of the saw blade can also be adjusted.
In general, the lateral pivotal position of the saw unit can be adjusted between a 0xc2x0 position and a 45xc2x0 position. In the 0xc2x0 position, the saw blade extends perpendicular to the base or the workpiece, so that a normal cutting operation can be performed. In the 45xc2x0 position, the saw blade is inclined at an angle of 45xc2x0 relative to the base or the workpiece. This 45xc2x0 position is most frequently selected when a laterally inclined (bevel) cutting operation is performed. This position is referred to as a xe2x80x9cstandard inclined positionxe2x80x9d in this description. A stopper device serves to prevent the saw unit from pivoting from the 0xc2x0 position to a position less than 0xc2x0 and also from pivoting from the 45xc2x0 position to a position more than 45xc2x0. Therefore, the operator can easily and reliably position the saw unit at either the 0xc2x0 position or the 45xc2x0 position.
U.S. Pat. Nos. 5,433,008 and 4,999,916 teach portable circular saws that have a stopper device to stop the inclination of the saw unit selectively at the standard inclined position and an extra inclined position, which may be an inclination angle of more than 45xc2x0.
FIG. 6 of U.S. Pat. No. 5,433,008 has been incorporated into the drawings of this application as FIG. 17. As shown in FIG. 17, a lateral inclining device 100 comprises an upright guide plate 102 that is secured to a base 101. An arc-shaped slot 103 is formed in the guide plate 102. A saw unit (not shown in FIG. 17) can pivot about a pivot shaft 105 and has a lock screw 104 that is inserted into the arc-shaped slot 103 and that can move along the arc-shaped slot 103. A stopper screw 107 is mounted on the guide plate 102 at one end of the arc-shaped slot 103 and opposes the lock screw 104. A disk member is rotatably mounted on the lock screw 104 and has legs 106 positioned on both sides of the lock screw 104.
In order to prevent the saw unit from pivoting more than an inclined angle 45xc2x0 (i.e., the standard inclined position), the disc is rotated to a position in which one of the legs 106 opposes the stopper screw 107. The operator pivots the saw unit, so that one of the legs 106 contacts the stopper screw 107 when the saw unit reaches the 45xc2x0 position. The operator thereafter tightens the lock screw 104, so that the saw unit can be fixed in position at the 45xc2x0 position.
In order to fix the saw unit at an extra inclined position that is past the 45xc2x0 position, the operator rotates the disk member by an angle of 90xc2x0 while the stopper screw 107 is disposed within an enlarged end portion 103a of the slot 103, so that the lock screw 104 directly opposes the stopper screw 107. As a result, the saw unit can be stopped at the extra inclined position as shown in FIG. 17, in which the lock screw 104 directly contacts the stopper screw 107.
FIG. 3 of U.S. Pat. No. 4,999,916 has been incorporated into the drawings of this application as FIG. 18. As shown in FIG. 18, a lateral inclining device 120 comprises an upright guide plate 124 that is secured to a base 121. A saw unit 123 can laterally pivot relative to the base 121 about a pivotal shaft 122. A bracket plate 125 also can pivot about the pivotal shaft 122.
A first guide slot 126 is formed in the guide plate 124 and extends along an arc about the pivotal shaft 122. A second guide slot 128 having a greater curvature than the first guide slot 128 is connected to the upper end of the first guide slot 126 via an L-shaped part 127.
The bracket plate 125 is mounted on the saw unit 123 and has an L-shaped slot 125a. A lock screw 129 is secured to the saw unit 123 and is inserted into the L-shaped slot 125a and the first guide slot at 127 (or the second guide slot 128).
In order to prevent the saw unit 123 from pivoting past an inclined angle of 45xc2x0 (i.e., the standard inclined position), the lock screw 129 is positioned on the left side within the L-shaped slot 125a. Therefore, the lock screw 129 can contact the upper end of the first guide slot 126. The saw unit 123 then can be fixed in the 45xc2x0 position by tightening the lock screw 129.
In order to stop the saw unit at an extra inclined position past the 45xc2x0 position, the operator shifts the lock screw 129 rightward within the L-shaped slot 125a with the lock screw 129 positioned at the upper end of the first guide slot 126 of the guide plate 124. As a result, the lock screw 129 moves into the second slot 128 via the L-shaped part 127. Therefore, the saw unit 123 can be stopped at the extra inclined position when the lock screw 129 contacts the upper end of the second slot 128.
However, in both the above U.S. patents, in order to change the stop position of the saw unit from the 45xc2x0 inclined position to the extra inclined position that is more than 45xc2x0, or from the extra inclined position to the 45xc2x0 inclined position, the operator must perform a cumbersome operation.
For example, in U.S. Pat. No. 5,433,008, in order to change the stop position, the disc must be rotated to change the position of the legs 106 with the stopper screw 104 positioned within the enlarged end portion 103a of the guide slot 103. Thus, the pivotal movement of the saw unit must be first stopped at about the 45xc2x0 inclined position and then the disc must be rotated to further pivotally move the saw unit.
In U.S. Pat. No. 4,999,916, in order to change the stop position, the lock screw 129 must be shifted from the first guide recess 126 to the second guide recess 128 or from the second guide recess 128 to the first guide recess 126 with the lock screw 129 positioned at about the upper end of the first guide recess 126, in which the saw unit 123 is inclined at an angle of about 45xc2x0.
It is, accordingly, one object of the present invention to teach portable circular saw having improved stopper devices, which can simplify the operation of changing the stop position.
In one aspect of the present teachings, portable circular saws are taught that can smoothly move from an inclined position less than 45xc2x0 to an inclined position more than 45xc2x0 without interruption or special operations. Thus, the saw unit can freely pivot through the 45xc2x0 position, when desired by the operator. However, the saw unit can also stop at the 45xc2x0 position when desired by the operator. Therefore, such portable circular saws are particularly convenient to use.
In another aspect of the present teachings, circular saws may have an engaging mechanism mounted on the base and adapted to engage a stopper that can move with a saw unit. The engaging mechanism can engage the stopper when the saw unit is in a first maximum inclined position (e.g., 45xc2x0) and when the saw unit is in a second maximum inclined position (e.g., 50xc2x0) that is greater in the incline angle than the first inclined position. Therefore, the operator can adjust the maximum inclined position without operating a mechanism associated with a lock screw, such as a disk member mounted on the lock screw, and without shifting the lock screw. As a result, the operator can smoothly incline the saw unit from an inclined position that is less than the first maximum inclined position, such as 45xc2x0, to the second maximum inclined position, such as 50xc2x0, via the first maximum inclined position without interruption of the inclining movement at the first maximum inclined position.